This invention relates generally to buckle-type folding machines and, more particularly, to the method and apparatus provided for positioning the rollers with respect to one another.
In buckle-type folding machines, several rollers cooperate with the series of fold plates to generate one or more folds in a previously unfolded sheet of paper. The rollers, typically from three to six in number, are arranged with their axes mutually parallel and in a zig-zag relationship, the angle formed by connecting three successive axis being approximately 90.degree.. The spacing between the adjacent rollers is such that when the rollers are driven with equal peripheral velocities, the combined driving action of two adjacent rollers will capture a leading edge of a piece of paper presented at the roller interface and convey it through the gap between the rollers.
The zig-zag arrangement results in a pocket being formed by each three successive rollers. Projecting into any or all of these pockets are fold plates. Each fold plate (a maximum in number of N-2 where N is the number of rollers) has a cavity, the opening of which is arranged to receive the leading edge of a piece of paper as it is conveyed toward the fold plate by the driving action of the first and second roller of a three-roller group. An adjustable stop permits the leading edge of the paper to penetrate the cavity to only a predetermined extent, whereupon the continued conveyance of trailing portion of the piece of paper causes the paper to buckle toward the interface between the second and third rollers of the three-roller group. The driving action of the second and third rollers results in the capture of the buckled portion of the paper, thereby generating a fold. Upon emerging on the other side of the second and third roller interface, the folded paper is conveyed into either another fold plate for an additional folding operation or a receiving tray for collection.
To perform the above-described conveying and folding operations, the spacing between the various rollers and between the rollers and the fold plates must be maintained to within close tolerances. The roller-to-roller spacing is critical in order to assure positive conveying action without subjecting the paper and rollers to excessive contact pressure therebetween. The roller-to-fold plate spacing is critical to assure that as the paper is conveyed toward a fold plate, it will be directed into the fold plate cavity and not between the fold plate and the roller periphery where it might jam. In addition, when non-resilient (e.g., metal) rollers are utilized, the rollers must be resiliently mounted to prevent jamming in the event multiple thicknesses of paper are introduced between two rollers.
Known roller positioning methods and apparatus are subject to several disadvantages. Typically, the ends of one or more of the rollers are journalled in either rocker arms or translating bearing blocks. Whichever is employed, the direction of travel of a given roller is generally along a radial line away from the next preceding roller. As a result, the direction of travel of the roller is at an angle, on the order of 45.degree., with the subjacent fold plate. Hence, any adjustment of the roller position necessarily affects the spacing between the roller periphery leading edge of the and the fold plate. The result is that the fold plate position must then be adjusted to restore the proper spacing between the roller surface and the fold plate leading edge. A further serious disadvantage of having the direction of travel form an oblique angle with the subjacent fold plate is that whenever multiple thicknesses of paper are inadvertently run between a set of rollers, the second roller, being resiliently mounted, may be displaced into an interfering relationship with the leading edge of the subjacent fold plate. Should this occur, serious damage to both the roller surface and the fold plate may result.
Accordingly, it is an object of the present invention to provide an adjustable roller positioning method and apparatus which has a resilient mounting feature but which nevertheless precludes the possibility of interference between the rollers and the leading edges of the fold plates in the event multiple thicknesses of paper are inadvertently conveyed between two rollers.
A related object of the present invention is to provide a roller positioning method and apparatus which permits ready adjustment of the spacing between the rollers without also requiring readjustment of the spacing between the rollers and the leading edges of the subjacent fold plates.
Still another object of the present invention is to provide a roller positioning system having standardized components to facilitate replacement of parts and repair of the apparatus.